The growth mechanism of thin Ge1-xMnx/Ge(100) diluted magnetic semiconductor films have been studied by reflection high energy electron diffraction (RHEED) technique and correlated to the structural and magnetic properties of the films provided by X-ray diffraction (XRD) and magneto-optical Kerr effect (MOKE), respectively. The RHEED analysis evidenced a transition from a bi-dimensional to a three-dimensional growth mechanism at deposition temperature, T-G, lower than 433 K while XRD characterization showed a polycrystalline structure with Ge grain size depending on T-G. At low T-G (343 K) all the Ge1-xMnx films behaved superparamagnetically, while at T-G = 433 K hysteresis loops were observed, with a maximum Curie temperature of approximate to 250 K, for 0.027 < x < 0.044. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.